var xml = <box xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <label value="hogehoge"/> <div xmlns="http://www.w3.org/1999/xhtml"> <p>abc</p> </div> </box>; xml.toXMLString() /* <box xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> </box>